The secure key rate considering data fluctuation and the finite data size effect is calculated following the theory [1]}:
\(\begin{split}R=&\frac{1}{N_t}\lbrace  n_1^\prime [1-H(e_1^{ph^\prime })]-fn_t^\prime H(E_Z)\rbrace \\&-2\log _2\frac{2}{\varepsilon _{cor}}-2\log _2\frac{1}{\sqrt{2}\varepsilon _{PA}\hat{\varepsilon }}\rbrace ,\\\end{split}\) 
